Water
GH and KH are different measurements
General hardness and carbonate buffering describe different aspects of water chemistry.
What GH adds
GH relates to dissolved minerals such as calcium and magnesium. It does not tell you how much ammonia is present or directly replace a KH or pH test.
Start with your source water
Use a freshwater test kit and record both the reading and units. Your water supplier’s information can provide context, but it is not the same as testing the water in a stocked pond.
Avoid unnecessary correction
Do not add mineral products simply because another keeper uses them. Check the needs of the species, current GH/KH/pH and what your regular water changes already supply.
Ask with a complete picture
When requesting advice, include source and pond readings, volume, maintenance routine and any salts or minerals already added. This prevents a recommendation based on an isolated number.
Keep GH separate from KH
Give each measurement its own column in your journal, with the kit and unit. If you are comparing a tap-water report with a pond kit, bring both documents to the discussion.
Sources & further reading
Original WakeyKoi wording, informed by the references below. Linked clinical resources explain the evidence and their scope; they have not reviewed or endorsed this website.
Related guides
Educational guidance cannot diagnose an individual fish. Breathing distress, severe injury or unexplained losses need prompt professional assessment.